Conventional bicycle wheel rims are manufactured from straight extruded sections of material, such as metal, which are cut, bent into a hoop shape and the ends bonded, welded or otherwise joined together. Alternatively, the wheel rims may be formed from a composite material such as carbon fibre reinforced plastic. Such rims are made directly into a hoop shape and so the above bending step is not required. In both of the above arrangements, the rim has a constant depth at all points around its perimeter. Spokes are then connected to various points around the radially inner surface of the wheel rim. Alternatively, the bicycle rim and spokes are formed integrally from composite materials.
In use, conventional wheel rims may suffer aerodynamic problems. For example, conventional wheel rim designs may result in a large amount of drag on the wheel, reducing the speed of the bicycle. Furthermore, movement of ambient air, travelling at a non-zero yaw angle relative to the general direction in which the bicycle is travelling, may cause a transverse resultant force to be applied to the wheel. If this force is applied at a location forward or rearward of the hub, the force will create a moment about the center of the wheel, which, in the case of the front wheel, will act to cause the wheel to steer away from the desired path. The rider must apply a steering input to counteract this. The point of action of this force on the wheel is known as the center of pressure. In particular, the center of pressure is defined as the point at which the moment about the vertical and horizontal axes in the plane of the wheel is zero (i.e. zero yaw and zero roll). This point is not applicable at zero yaw since the side force is effectively zero.